Rear end of a vehicle body

ABSTRACT

An improved rear end design for a vehicle body including a first, upper cross member and a second, lower cross member fitted one over the other to form a compound beam. Each cross member is preferably formed as an aluminum extrusion. The upper cross member has the same contour shape as the lower edge of the access door for the trunk. The lower cross member lies below the level of the trunk floor and includes a middle region contour having a curve which matches a corresponding overlying middle region of the upper cross member. Each side end of the lower cross member curves forward under the trunk floor and is joined to a corresponding end of a pair of transversely spaced longitudinal side bearer members or impact-absorption units. The invention provides for a stable rear-end construction, particularly at the joints with the rear impact-absorption units, and also forms a support edge for the trunk-access door. The invention also results in less extensive repairs in the event of a rear collision.

FIELD

The present invention relates generally to a vehicle body structure, andmore particularly to an improved rear end design of a vehicle body whichis both stable and easily repairable.

BACKGROUND

In sheet metal vehicle bodies, the rear end is typically assembled bywelding together a number of preformed metal sheets to form a bearingstructure having an encasing outer wall. In most instances, a crossmember is provided for connection to both the floor of the trunk and tothe ends of the longitudinal bearers in the region where they emergeinto the rear end portion of the vehicle body.

Such a construction is relatively costly, due to the larger number ofsheet metal parts and welding steps required. Furthermore, since theentire interconnected arrangement is usually deformed in the event of arear collision, repair costs are also expensive and cost-intensive.

In known rear end designs of the type comprising a pair of transversemembers including an upper transverse member and a lower transversemember joined together one above the other, and wherein the transversemembers each have a constant cross section and the lower transversemember is joined to a trunk floor, a substantial portion of the lowertransverse member contour lies above the level of the trunk floor. Inaddition, the lengthwise members provided on each side of the vehicleterminate in the region in front of the rear wheel housings. Since therear end is joined by many structural pieces to the wheel housings, sidewalls, helical springs, etc., the impact energy associated with acommonly occurring rear collision from a sideways directioncorrespondingly acts on a number of parts, including the load-bearingframe elements. Thus, even a vehicular collision of a relatively lowimpact energy will cause major damage, thereby resulting in high repaircosts for straightening out and replacing the many damaged sheet metalcomponents.

U.S. Pat. No. 1,809,606 discloses a vehicle frame structure wherein twolongitudinal members are joined by rivet connections by a middle crossmember and a rear cross member. The middle cross member has curved ends,each of which abut on one of the opposing inward facing walls of the twolongitudinal members. The rear cross member is straight and is flushmounted at right angles to the rear ends of the longitudinal members.

Other arrangements for the load bearing frame elements of a vehiclespace frame are known, such as, for example, from InternationalPublication No. WO 90/02680 (corresponding to International ApplicationNo. PCT/NO89/00086), wherein each load bearing longitudinal structuralmember is formed as an integral extruded multicavity shape which issplit, selectively curved, and aligned to merge with secondarycomplementary shaped members. A portion of each of the multicavityshaped members diverges from the longitudinal direction to form frontand rear cross members, however, no compound cross member having meansfor reducing impact energy is disclosed or suggested.

Repairs are especially problematic for the known vehicle bodies whichhave space frames assembled from extruded aluminum sections and castjoint elements, an example of which is disclosed in European patentdocument EP 0 146 716. Such aluminum bodies are extremely long-lived onaccount of the increased resistance to corrosion as compared toconventional sheet metal bodies. Based on present day accidentstatistics, it is safe to assume that such long-lived vehicle bodieswill likely experience repeated damage with deformations, especially inthe rear end, during the average course of its lifetime. Repairs,especially repairs of the aluminum load-bearing frame elements, areparticular problematic on account of the known difficulties, such asexpensive light metal welds and loss of strength at welded points in thecase of multiple welds. Therefore, it is desirable to provide structuralsolutions which protect against damage caused to the vulnerablecollision points of the load-bearing frame elements in a light-metalvehicle body particularly in the event of commonly occurring minorcollisions having less serious impact energies.

THE INVENTION Objects

It is therefore a principle object of the present invention to providean improved rear end design for a vehicle body comprising a rearcompound cross beam member arrangement which provides a stable bearingstructure including a lower cross member for support of the trunk floorand an upper cross member having a rearwardly protruding portiondisposed adjacent a bumper arrangement such that impact energies arefirst absorbed by the upper cross member thereby sparing the lower crossmember of deformation in the event of a rear impact.

It is another object of the present invention to provide an improvedrear end design for a vehicle of the type described which is of simpleconstruction and is less costly to repair in the event of a rearcollision.

Other and further objects will become evident from the followingdrawings, written description and appended claims.

DRAWINGS

The invention is explained with additional details, features, andadvantages by means of a sample embodiment in which:

FIG. 1 is a perspective view of part of a rear body of a vehicle; and

FIG. 2 is a section view taken along line A-A and in the direction ofarrows of FIG. 1.

SUMMARY

According to the invention, a compound rear cross member assemblycomprising an upper and lower cross member is provided for joiningtogether the lengthwise members of the vehicle frame in the region wherethey extend into and terminate at the rear zone of the vehicle body. Thelower cross member is situated beneath the level of the trunk floor andincludes a middle portion having a contour which corresponds to anoverlying middle contour portion of the upper cross member. The ends ofthe lower cross member are forwardly curved beneath the trunk floor andare joined to the corresponding longitudinal bearers in abuttingfashion. The upper and lower cross members are joined together at theiroverlying middle contour regions. The connection between the upper andlower cross members creates a stable compound beam.

In this simple compound beam arrangement, the upper cross member of thecompound beam travels along the outer edge above the floor of the trunkand forms the supporting edge surface for the trunk-access door. At thesame time, the lower cross member provides a suitable bridgingconnection for joining together the ends of the longitudinal memberswhereby the curved ends facilitate good force distribution to thelongitudinal members. Since the curved ends of the lower cross membertravel beneath the floor of the trunk, this arrangement does not affectthe desired level trend of the trunk floor.

Also, as each end of the lower cross member is heavily curved forward,the lower cross member is the last portion of the compound beam todeformed, if at all, in a side angle rear collision. With a suitablearrangement of the bumper, only the upper cross member will sufferdamage in a rear impact of lesser severity, thus allowing for easyreplacement of only the upper cross member during repairs. The inventionis especially easy to fabricate with extruded aluminum sections, inwhich case the longitudinal members are also preferably formed asextruded aluminum sections.

To ensure a stable connection between the two cross members, it isrecommended that they be secured by welding. However, with properdimensioning and provision of sufficiently large supporting surfaces,glue adhesives may be used to bond the compound beam together,preferably with a positive interlocking connection. Alternatively, anddepending on the design, the desired connection may also be made byscrew, bolt and other like mechanical fasteners.

In modern vehicles, the rear end portion of the longitudinal bearerstypically carry impact-absorption units on which the bumpers or bumperbearers are mounted. Since this region represents a connection point ofthe bearing structure which requires a stable design, the inventionproposes to connect the ends of the lower cross member to theseconnection points or to the rear impact-absorption units to provide fora firm structure. Preferably, this joint should also be made by welding.

A favorable geometrical arrangement is realized if the lower crossmember is situated approximately at the height of the bumper bearer sothat the ends of the longitudinal bearers or impact-absorption units arepositioned at the height of the lower cross member. Each end of thelower cross member is preferably welded in abutment with one of at theopposed inward facing side surfaces of the corresponding end portions ofeach longitudinal bearer such that the cross member bridges the ends ofthe longitudinal members.

In another embodiment of the invention, the length of the upper crossmember extends a distance beyond the outward edge of the longitudinalbearers to facilitate the fabrication of a rear end having a substantialcurving outer body side contour with suitable shaped contoured elementsfor the rear end.

In a specific embodiment of the invention, the lower cross member isformed as an L-shaped hollow section. In this way, it is easy to supportthe trunk floor on the lower, horizontal leg of the L-structure forconnection thereto. The upper, vertical leg provides a suitable bearingsurface for the upper cross member. The L-structure configurationprovides for a lower cross member which exhibits high rigidity.

The upper cross member is preferably formed as a single extrusioncomprising a first upper triangular hollow section and an adjoiningsecond lower portion designed as a flat vertical plate having ahorizontal ridge member at a bottom end thereof for connection to thelower cross member.

A sealing flange adapted for installation of a trunk seal or gasketmember may be conveniently formed on the upper triangular hollowsection, especially if it is formed as an extruded section.

In the preferred embodiment, the triangular hollow section of the uppercross member is projected in the rearward direction with respect to thevertical plate of the lower section such that a free space is createdbetween the bumper and/or the upper edge of the bumper in the region ofthe vertically flat plate. The concave bulge of the bumper alsosurrounds the lower cross member with a free space. Thus, in the eventof low energy rear impact, the bumper when deformed will not, in turn,deform the transverse compound beam, such that only the familiar impactabsorption units operate in the free space and return the bumper to itsoriginal position after the impact.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what wepresently believe is the best mode of carrying out the invention.

FIG. 1 shows a portion of a rear end 1 of a vehicle body which includesa trunk floor 2 provided with a spare wheel recess 3. A pair oflaterally spaced longitudinal members 4 (only one of which is shown) aredisposed along opposing sides of the trunk floor 2. Each rearwardlydisposed end of longitudinal members 4 includes an impact-absorptionunit 5. The impact absorption units 5 are bridged together by a compoundbeam consisting of an upper cross member 6 and a lower cross member 7.

The upper and lower cross members 6, 7 are preferably formed as extrudedaluminum sections. As is best seen in the cross section view of FIG. 2,the lower cross member 7 is formed as an L-shaped hollow section. Therear perimeter edge of the trunk floor 2 rest against a first horizontalleg 8 of the L-shaped cross section 7 while the upper, vertical leg 9provides a bearing surface for supporting the upper cross member 6.

The upper cross member 6 includes an upper triangular hollow shapeportion 10 and an adjoining lower flat plate portion 11. The lower flatplate portion 11 is provided with a horizontal leg 12 at its bottom endfor connection to the vertical leg 9 of the lower cross member 7.

The preferred method for connection of the horizontal leg 2 to thevertical leg 9 is by welding, however it is understood that other knownconnection techniques may be used, including but not limited toconnection by glue adhesives, or connection by rivets, screw fastenersand other like mechanical fastening means.

In the resulting compound beam, the contour of the upper cross member 6follows the slight curvature of the lower supporting edge of thetrunk-access door 13. In the upper region of the upper cross member 6 ona side facing the access door 13 a corresponding sealing flange 14 ispreferably molded on the triangular hollow shape 10 and is provided witha trunk-access door seal 15. Rear body elements 16 are adjoined to theside ends of the upper cross member 6 in conventional fashion.

The lower cross member 7 lies beneath the level of the trunk floor 2 andits middle region follows the slight curvature of the upper cross member6, where it is also firmly joined to the latter. The side ends 17, 18 ofthe lower cross member 7 are heavily curved forward and are connected inabutting fashion to the impact-absorption units 5 to form stablejunction points.

The cross section view of FIG. 2 also illustrates the position andarrangement of a bumper 19 which comprises a bumper bearer 20 and acover 21. The triangular hollow shape 10 of the upper cross member 6projects to the rear relative to the adjoining lower, vertical plateportion 11. The upper edge 22 of the bumper 19 is disposed to lie bothbehind and underneath the triangular hollow shape 10 such that a freespace is formed in the rear region adjacent the vertical plate 11. Theconcave bulge of the bumper 19 surrounds the lower cross member 7 at adistance sufficient to create a free space necessary for the safetyoperation of impact absorbers, whereby the bumper 19 is held in place bythe impact-absorption units 5 via the rear body elements 16 in the knownway.

The unique compound beam arrangement of the cross members 6 and 7provides both a support for the trunk-access door (in upper cross member6) and forms stable junction points which exhibit good forcedistribution characteristics in the region of the impact-absorptionunits. In the event of a rear impact of moderate severity, it is likelythat only the upper cross beam 6 will suffer damage. Accordingly, boththe damage and the repair cost of the present invention is less thanthat of familiar configurations.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. We therefore wish our invention to bedefined by the scope of the appended claims as broadly as the prior artwill permit, and in view of the specification if need be.

PARTS LIST

1. Rear End

2. Trunk Floor

3. Spare Wheel Recess

4. Lateral Longitudinal Member

5. Impact-Absorption Unit

6. Upper Cross Member

7. Lower Cross Member

8. Horizontal Leg Portion

9. Vertical Leg Portion

10. Upper Triangular Shape Portion

11. Lower Flat Plate Portion

12. Horizontal Leg

13. Trunk-Access Door

14. Sealing Flange

15. Seal

16. Rear Body Elements

17. Forwardly Curved Side End

18. Forwardly Curved Side End

19. Bumper

20. Bumper Bearer

21. Cover

22. Upper Edge

We claim:
 1. In a vehicle body rear end which includes a pair oftransversely spaced longitudinal bearers each having animpact-absorption unit disposed at a rearward end portion thereof, atrunk floor interposed between said longitudinal bearers and atrunk-access door, an improved rear end bearing structure comprising inoperative combination:a) a lower cross member disposed beneath the levelof the trunk floor having a middle region and opposed ends, each of saidends being forwardly curved and joined in abutment with a correspondingimpact-absorption unit of said pair of longitudinal bearers; b) an uppercross member disposed on top of said lower cross member and having amiddle region aligned with said middle region of said lower cross memberand a pair of ends on which are supported outwardly disposed rear bodyelements, said upper cross member having a contour forming a lowersupporting edge of the trunk-access door; and c) means for connectingsaid middle portions of said upper and lower cross members to form acompound beam.
 2. A rear end in a vehicle body as in claim 1 whereinsaid upper and lower cross member are formed as extruded light metalsections.
 3. A rear end in a vehicle body as in claim 1 wherein saidconnection means comprises a welded joint connection.
 4. A rear end in avehicle body as in claim 2 wherein said connection means comprises anadhesively bonded joint connection.
 5. A rear end in a vehicle body asin claim 2 wherein said connection means comprises mechanical fasteners.6. A rear end in a vehicle body as in claim 2 wherein:a) said lowercross member is formed as a hollow L-shaped profile in cross sectionincluding a lower, horizontal leg and an upper, vertical leg andwherein:i) said lower, horizontal leg supports at least a portion ofsaid trunk floor; and ii) said upper, vertical leg supports said middleregion of said upper cross member.
 7. A rear end in a vehicle body as inclaim 6 wherein said upper cross member comprises an upper triangularhollow portion in cross section and includes an adjoining lowervertically oriented flat plate portion, said flat plate portion having atransverse horizontal ridge disposed at a bottom edge thereof forconnection to said lower cross member middle portion.
 8. A rear end in avehicle body as in claim 7 wherein said upper cross member includes aflange disposed along an upwardly and rearwardly facing surface of saidupper triangular hollow portion, said flange adapted for carrying asealing element for the trunk-access door.
 9. A rear end in a vehiclebody as in claim 8 wherein said triangular hollow portion of said uppercross member projects rearwardly with respect to said flat portion suchthat a free space is created by the surrounding enclosure of said lowercross member by a bumper assembly disposed rearwardly adjacent saidupper cross member.
 10. A rear end in a vehicle body as in claim 8wherein said connection means comprises a welded joint connection.
 11. Arear end in a vehicle body as in claim 8 wherein said connection meanscomprises an adhesively bonded joint connection.
 12. A rear end in avehicle body as in claim 8 wherein said connection means comprisesmechanical fasteners.
 13. A rear end in a vehicle body as in claim 9wherein said connection means comprises a welded joint connection.
 14. Arear end in a vehicle body as in claim 9 wherein said connection meanscomprises an adhesively bonded joint connection.
 15. A rear end in avehicle body as in claim 9 wherein said connection means comprisesmechanical fasteners.
 16. In a rear end of a light metal vehicle bodyincluding a pair of transversely spaced longitudinal bearers each havingan impact-absorption unit disposed at a rearward end portion thereof, atrunk floor interposed between said longitudinal bearers and atrunk-access door, an improved rear end bearing structure comprising inoperative combination:a) an extruded light metal lower cross memberdisposed beneath the level of the trunk floor having a middle region andopposed ends, each of said ends being forwardly curved and joined inabutment with a corresponding impact-absorption unit of said pair oflongitudinal bearers; b) an extruded light metal upper cross memberdisposed on top of said lower cross member and having a middle regionaligned with said middle region of said lower cross member and a pair ofends on which are supported outwardly disposed rear body elements, saidupper cross member having a contour forming a lower supporting edge ofthe trunk-access door; and c) means for connecting said middle portionsof said upper and lower cross members to form a compound beam.
 17. Arear end in a vehicle body as in claim 16 wherein:a) said lower crossmember is formed as a hollow L-shaped profile in cross section includinga lower, horizontal leg and an upper, vertical leg and wherein:i) saidlower, horizontal leg supports at least a portion of said trunk floor;and ii) said upper, vertical leg supports said middle region of saidupper cross member.
 18. A rear end in a vehicle body as in claim 17wherein said upper cross member includes a flange disposed along anupwardly and rearwardly facing surface of said upper triangular hollowportion, said flange adapted for carrying a sealing element for thetrunk-access door.
 19. A rear end in a vehicle body as in claim 18wherein said triangular hollow portion of said upper cross memberprojects rearwardly with respect to said flat portion such that a freespace is created by the surrounding enclosure of said lower cross memberby a bumper assembly disposed rearwardly adjacent said upper crossmember.
 20. A rear end in a vehicle body as in claim 19 wherein saidconnection means comprises a welded joint connection.